Concrete is a common building material that is prized for its versatility, strength and durability. However, strength and durability are both compromised in concrete due to damage as a result of water intrusion through cracks, which in turn leads to various destructive processes within concrete—especially concrete containing steel reinforcement. Since concrete is a mixture of various components, including water, and is weak under tension, it is common for concrete to develop cracks due to tension forces caused by shrinking and/or loading. Such resulting cracks provide paths for the easy intrusion of water and waterborne chemicals, which commonly lead to damaging chemical and physical processes and premature deterioration of the concrete.
It has been observed that some cracks in concrete may initially allow the passage of water, but then over time, the flow of water may be reduced and eventually stopped completely. A crack, that formerly allowed the passage of water and subsequently sealed so as to no longer allow the passage of water, is said to have “self-sealed”.
Chemical agents are commercially available which claim to enhance the ability of concrete to self-seal. These agents further claim that they allow concrete to self-seal more quickly and also allow self-sealing of cracks that are much wider than those cracks that may self-seal in concrete that do not contain these agents.
Accordingly, a need exists for a method for testing the self-sealing properties of a concrete sample in order to prove or disprove the claims made about these agents. In addition, a reliable test method would allow for the comparison of concrete mixtures, which vary in their ingredients, proportions and other factors contributing to their hardened properties, in so far as these relate to the self-sealing ability of the concrete.
A suitable method for testing the self-sealing properties of a concrete sample has not previously existed. Prior art relating to this subject has failed to achieve acceptable results due to two major missing elements:                1. The ability to produce a concrete sample with consistent, predictable and repeatable crack size and shape. The ability to produce a crack with the same size and shape in each concrete sample is critical to the comparability and validity of test results measured and compared between samples; and        2. The ability to produce a suitable flow of water through a crack in a concrete sample that is consistent between comparable samples, can be accurately measured over time and maintains a constant vertical head pressure over time, independent of flow.        
It is an object of the present invention to address these two missing elements. Other objects of the invention will be apparent from the description that follows.